fossilfandomcom-20200214-history
Eurotrochilus
Eurotrochilus is a genus of extinct members of the stem group Trochilidae and are the closest relatives of the crown group Trochildae, which includes modern hummingbirds.3 Despite Eurotrochilus having looked very similar to modern hummingbirds, they still retained several primitive features and are not closely related to any specific extant hummingbird in the crown group.4 There are currently two discovered species of Eurotrochilus- E. inexpectatus1 and E. noniewiczi.2 Eurotrochilus has been dated back to the Rupelian age of the early Oligocene era, which occurred during the Paleogene period. While there is some debate over exactly when Eurotrochilus was present, the most recent estimate is suggested to be 28 to 34 million years ago.2 The discovery of Eurotrochilus fossils in Germany, France, and Poland was extremely important because today all 328 of the extant species of hummingbirds only occur in the New World but the fossils of Eurotrochilus suggest an Old World origin.5 Extant hummingbirds are distinctly different than all other avains because of their unique adaptions for hovering flight and nectarivory.4 Like extant hummingbirds, Eurotrochilus has these adaptions and are the only genus of stem group Trochildae to do so. Etymology The name Eurotrochilus is derived from the location and family of the fossils found. Euro stands for Europe, the continent where the holotype specimen was found, and Trochilus is representative of the type family of the modern Trochilidae.1 The species name E. inexpectus is Latin for “unexpected”, indicative of the surprise felt by Gerald Mayr and his team when they discovered a modern-type fossil Hummingbird in Europe.1 The name of the second species, E. noniewiczi, is acquired from the surname of the private collector, Edward Noniewicza, who found the fossil specimen. Description and Paleobiology Eurotrochilus specimens are some of the smallest fossil birds1 and are in the Apodiforme order of Aves due to their strongly abbreviated humeri and ulnae.2 They are most similar to another Apodiforme, an early Oligocene member of the stem-group Trochilidae, Jungornis.6 Both Eurotrochilus and Jungornis have morphological adaptations for sustained hovering flight, a characteristic of extant hummingbirds,6 including the Apodifmore synapomorphy (abbreviated ulna and humerus) as well as pronounced distal protrusions on the humeral heads.1 These adaptions in Eurotrochilus are more pronounced though. Another difference is that Eurotrochilus have elongated beaks (unknown in Jungornis1), which is evidence of nectarivory, the ability to consume nectar from flowers. Eurotrochilus are believed to be the first members of stem group Trochilidae to be able to perform nectarivory. Eurotrochilus are more closely related to crown group Trochilidae than other members of stem group Trochilidae, like Jungornis, because of their specific adaptations for both nectarivory and hovering flight. Nectarivory Adaptions In some species of Eurotrochilus, the skull and beak have been roughly measured to be 34 millimeters.2 The beaks of Eurotrochilus are greatly elongated, straight, and narrow, measuring from 15.5 to 20 millimeters in length, roughly 2.5 times as long as the cranium.15 This beak shape is distinctly different than other known beak shapes of early Tertiary stem-group hummingbirds, which were short, wide, and most likely used for eating insects as opposed to nectar.1 The maxillary processes of the palatine bones in the beaks of Eurotrochilus are widely separated, indicating the presence of rhynchokinesis, or the ability to flex the upper beak.1 In addition, Eurotrochilus appear to have long nasal openings and large hyoid bones.5 The large hyoid bones are thought to support a long protractile tongue, which extant hummingbirds use to lap up nectar.5 All of these adaptations made it possible for Eurotrochilus to consume nectar from Ornithophilous flowers, its main source of nutrients, and to pollinate these flowers as well. Hovering Flight Adaptions Hummingbirds have specific morphological adaptations that enable them to fly forwards, backwards, sideways as well as hover for extended periods of time.7 Hovering flight specifically is supported in Eurotrochilus by abbreviated ulnae and humeri and developed humeral protrusions. The ulna of Eurotrochilus measures between 6.7 and 8.8 millimeters, which is shorter than the ulna of Jungornis, which measures 13 millimeters.5 While Jungornis and Eurotrochilus both have abbreviated ulnas, the extreme abbreviation in Eurotrochilus supports monophyly of the clade that includes only Eurotrochilus and crown-group Trochilidae.1 Another synapomorphy of Eurotrochilus and crown-group Trochilidae includes the presence of deep fossa, or depressions, on the caudal surface of the proximal end of the ulnae.6 The humeri of Eurotrochilus have been measured to be between 6.0 and 6.5 millimeters.2 It is considered short and stout when compared to other Apodiformes, except extant hummingbirds. In addition, the humeri have a wide proximal articular part2 and there are pronounced distal protrusions on the caput humeri, which is a synapomoprhy of Jungornis, Eurotrochilus, and crown group Trochilidae.6 The humeri protrusions in Eurotrochilus are significantly more marked than in Jungornis and are more similar to Trochilidae.1 These morphological specializations of the humeri allow the bone to rotate during hovering flight.4 Additional adaptions present for hovering flight in both groups include curved and relatively short wings, square-shaped tails,5 and a column like sternal end of coracoid with a convex dorsal surface. Primitive Features Despite the similarities between the two, crown group Trochilidae has a more derived morphology than Eurotrochilus, showing Eurotrochilus to be a stem group representative.1 These more primitive morphologies in Eurotrochilus include the bones of the hand (carpometacarpus and distal phalanges) being longer than the ulna, the carpometacarpus lacking a dentiform process, and the presence of a small intermetacarpal process.1 Scientists are confident though with the assignment of Eurotrochilus to stem group Trochilidae as there has been no identification of derived characteristics that would cause Eurotrochilus to be assigned to any other taxa of aves. Discovery and classification Category:Prehistoric birds of Europe Category:Oligocene birds Category:Poland